This invention relates to a power operated positioning apparatus for moving and locating a work piece with respect to selected positions.
Various apparatus have been provided for selectively moving workpieces during a machining, welding, or other operation. Most of these apparatuses have incorporated fluid operated actuators such as hydraulic or pneumatic operated piston and cylinder actuators. While these fluid operated actuators are generally satisfactory when moving workpieces with respect to a stationary support, difficulties arise in using actuators of this type in non-stationary support situations such as moving transfer devices, conveyors, shuttles, or the like. In addition, the use of hydraulic fluid in non-stationary applications can be the source of hydraulic fluid leaks while the use of pneumatic actuators increases cost of operation by requiring the production of sufficient quantities of compressed air of predefined quality for operating the apparatuses. Compressed air generally requires the use of fixed or flexible conduits to communicate the compressed air with the actuator and may produce compressed air leaks increasing operating costs. Further, hydraulic and pneumatic actuated workpiece positioning apparatuses require complex control mechanisms to adjust the rate of actuation of the apparatus to eliminate or reduce the amount of shock absorbed as the apparatus reaches a selected position.
In an effort to overcome the noted disadvantages of fluid operated actuators, various forms of workpiece positioning apparatus have been proposed utilizing an electrical power source. However, the prior art electric powered workpiece positioning apparatuses have been unduly complicated and expensive in construction, imprecise in operation, or unreliable in use.